Trunk piston engine lubricating oil compositions

ABSTRACT

A trunk piston engine lubricating oil composition is disclosed comprising (a) a major amount of a base stock containing at least 90% by weight saturated hydrocarbons; and (b) a base stock selected from the group consisting of (i) an ester base stock wherein the ester base stock is present in an amount greater than 10% by weight and no greater than about 45% by weight, based on the total weight of the lubricating oil composition, and (ii) an alkylated aromatic base stock.

This application is a Continuation of U.S. patent application Ser. No.12/803,491, filed Jun. 29, 2010. The foregoing related patentapplication, in its entirety, is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention generally relates to trunk piston enginelubricating oil compositions.

2. Description of the Related Art

Trunk piston engines operate using various types and qualities of dieselfuels and heavy fuel oils. These fuels typically contain highconcentrations of asphaltenes, generally the heaviest and most polarfraction of petroleum distillate. Asphaltenes are highly complexcompounds believed to be composed of polyaromatic sheets containingalkyl side chains, and are generally insoluble in lubricating oils. Whenheavy fuel oils and conventional lubricant oil compositions mix indifferent temperature regions of a trunk piston engine, black sludge(such as asphaltene deposits or other deposits) and other asphaltenederived deposits (such as undercrown deposits) tend to form. Theformation of black sludge or deposit can adversely affect the serviceinterval and maintenance cost of the trunk piston engine.

Presently, there is a move in the industry in different regions of theworld to replace Group I base oils with Group II base oils in trunkengine oils. Group II base oils generally have a lower aromatic contentthan Group I base oils, thereby resulting in a loss of heavy fuel oil(also known as residual fuel oil) compatibility when Group II or higherbase oils are used in trunk piston engine lubricating oils rather thanGroup I base oils. It is believed that this loss of heavy fuel oilcompatibility is due to the much lower solubility of asphaltenes in theGroup II or higher base oils compared to Group I base oils. Generally,the problem of the loss of heavy fuel oil compatibility has beentypically addressed by increasing the amount of detergent-containingtrunk piston engine lubricating oil additive packages.

U.S. Patent Application Publication No. 20080039349 (“the '349application”) discloses a lubricating oil composition containing (a) anoil of lubricating viscosity; (b) at least one overbased metaldetergent; and (c) at least one substituted diaryl compound. The '349application further discloses that the lubricating oil compositionexhibits improved asphaltene dispersancy in a trunk piston dieselengine.

U.S. Patent Application Publication No. 20090093387 (“the '387application”) discloses a lubricating oil composition containing (a) aGroup II basestock, and (b) a neutral or overbased metalhydrocarbyl-substituted hydroxybenzoate detergent having a basicityindex of less than 2. The '387 application further discloses that theneutral or overbased metal salicylate detergent having a basicity indexof less than 2 improves asphaltene dispersancy in Group II basestocks.U.S. Patent Application Publication No. 20090281009 (“the '009application”) discloses a lubricating oil composition comprising: (a) amajor amount of a Group I base oil and/or a Group II base oil; and (b)at least one detergent comprising a salt of an alkyl-substitutedhydroxybenzoic acid, wherein at least 90% of the alkyl groups are C₂₀ orgreater, wherein the lubricating oil composition is a medium or highsoap formulation. The '009 application further discloses that thecomposition exhibited less black sludge formation, better stabilityagainst oxidation-based viscosity increase and improved detergencyproperties in low sulfur marine residual fuels than lubricating oilcompositions containing a conventional salicylate-based detergent.

U.S. Patent Application Publication No. 20090291869 (“the 869application”) discloses a a trunk piston marine engine lubricating oilcomposition comprising (a) a Group II basestock, and, (b) an overbasedmetal hydrocarbyl-substituted hydroxybenzoate detergent having abasicity index of 5.5 or greater; and (c) an overbased metalhydrocarbyl-substituted hydroxybenzoate detergent having a basicityindex of 2 or less, wherein the ratio of the mass of metal in detergent(b) to the mass of metal in detergent (c) is 10 or less; the trunkpiston marine engine lubricating oil composition having a TBN (usingASTM D2896) of 20 to 60. The '869 application further discloses that thecomposition improves asphaltene dispersancy in Group II basestocks.

U.S. Patent Application Publication No. 20090291870 (“the 870application”) discloses a trunk piston marine engine lubricating oilcomposition comprising (a) a Group II basestock, and, (b) an overbasedmetal hydrocarbyl-substituted hydroxybenzoate detergent having abasicity index of 5.5 or greater; and (c) an overbased metalhydrocarbyl-substituted hydroxybenzoate detergent having a basicityindex in the range of 2.1 to 5.4, wherein the ratio of the mass of metalin detergent (b) to the mass of metal in detergent (c) is 1 or less; thetrunk piston marine engine lubricating oil composition having a TBN(using ASTM D2896) of 20 to 60. The '870 application further disclosesthat the composition improves asphaltene dispersancy in Group IIbasestocks.

U.S. Patent Application Publication No. 20100062957 discloses a methodof reducing asphaltene precipitation (black paint) in an engine, themethod including the step of lubricating the engine with a lubricatingoil composition comprising, or made by admixing: (a) an oil oflubricating viscosity in a major amount; and (b) a salicylate detergentsystem in a minor amount comprising one or more neutral or overbasedalkaline earth metal C₂₂ hydrocarbyl substituted salicylates; with theproviso that the salicylate detergent system does not include an alkalimetal salicylate.

WO2008102114 (“the '114 application”) discloses a liquid lubricant baseoil composition useful for a 2-stroke marine diesel engine cylinder oil,a 2-stroke marine diesel engine system oil, and a 4-stroke marine dieselengine. The lubricant base oil composition disclosed in the '114application contains (a) a base stock comprising at least 95 wt. %saturated hydrocarbons, and (b) 0.2 to 30 wt. % of an aromatic(brightstock) extract. A bright stock is a high viscosity base oil whichhas been conventionally produced from residual stocks or bottoms and hasbeen highly refined and dewaxed. The '114 application further disclosesthat the combination of a Group II base oil and a low polycyclicaromatic brightstock extract demonstrated improved viscosity ratio andimproved oxidation and wear performance.

It would be desirable to develop a trunk piston engine lubricating oilcomposition which exhibits improved heavy fuel compatibility.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the present invention, a trunkpiston engine lubricating oil composition is provided comprising (a) amajor amount of a base stock containing at least 90% by weight saturatedhydrocarbons; and (b) a base stock selected from the group consisting of(i) an ester base stock wherein the ester base stock is present in anamount greater than 10% by weight and no greater than about 45% byweight, based on the total weight of the lubricating oil composition,(ii) an alkylated aromatic base stock, (iii) a base stock having anaromatic content of at least about 50% by weight, wherein the base stockhaving an aromatic content of at least about 50% by weight is not anaromatic extract, and mixtures thereof.

In accordance with a second embodiment of the present invention, a trunkpiston engine lubricating oil composition is provided comprising (a) amajor amount of a base stock containing at least 90% by weight saturatedhydrocarbons; and (b) a base stock selected from the group consisting of(i) an ester base stock wherein the ester base stock is present in anamount greater than 10% by weight and no greater than about 45% byweight, based on the total weight of the lubricating oil composition,(ii) an alkylated aromatic base stock, (iii) a base stock having anaromatic content of at least about 50% by weight, wherein the base stockhaving an aromatic content of at least about 50% by weight is not anaromatic extract, and mixtures thereof, wherein base stock (b)(ii) isdifferent than base stock (b)(iii).

In accordance with a third embodiment of the present invention, a trunkpiston engine lubricating oil composition is provided comprising (a) amajor amount of a base stock containing at least 90% by weight saturatedhydrocarbons; and (b) a base stock selected from the group consisting of(i) an ester base stock wherein the ester base stock is present in anamount greater than 10% by weight and no greater than about 45% byweight, based on the total weight of the lubricating oil composition,(ii) an alkylated aromatic base stock, (iii) a base stock having anaromatic content of at least about 50% by weight, wherein the base stockhaving an aromatic content of at least about 50% by weight is not anaromatic extract, and mixtures thereof, wherein the trunk piston enginelubricating oil composition is substantially free of a Group I base oil.

In accordance with a fourth embodiment of the present invention, thereis provided a method for improving heavy fuel oil compatibility of atrunk piston engine lubricating oil composition comprising a majoramount of a base stock containing at least 90% by weight saturatedhydrocarbons, the method comprising adding to the trunk piston enginelubricating oil composition a base stock selected from the groupconsisting of (i) an ester base stock wherein the ester base stock ispresent in an amount greater than 10% by weight and no greater thanabout 45% by weight, based on the total weight of the lubricating oilcomposition, (ii) an alkylated aromatic base stock, (iii) a base stockhaving an aromatic content of at least about 50% by weight, wherein thebase stock having an aromatic content of at least about 50% by weight isnot an aromatic extract, and mixtures thereof.

In accordance with a fifth embodiment of the present invention, there isprovided a method for operating a trunk piston engine comprisinglubricating the trunk piston engine with a trunk piston enginelubricating oil composition comprising (a) a major amount of a basestock containing at least 90% by weight saturated hydrocarbons; and (b)a base stock selected from the group consisting of (i) an ester basestock wherein the ester base stock is present in an amount greater than10% by weight and no greater than about 45% by weight, based on thetotal weight of the lubricating oil composition, (ii) an alkylatedaromatic base stock, (iii) a base stock having an aromatic content of atleast about 50% by weight, wherein the base stock having an aromaticcontent of at least about 50% by weight is not an aromatic extract, andmixtures thereof.

In accordance with a sixth embodiment of the present invention, the useof a base stock selected from the group consisting of (i) an ester basestock wherein the ester base stock is present in an amount greater than10% by weight and no greater than about 45% by weight, based on thetotal weight of the lubricating oil composition, (ii) an alkylatedaromatic base stock, (iii) a base stock having an aromatic content of atleast about 50% by weight, wherein the base stock having an aromaticcontent of at least about 50% by weight is not an aromatic extract, andmixtures thereof for the purpose of improving heavy fuel oilcompatibility of a trunk piston engine lubricating oil compositioncomprising a major amount of a base stock containing at least 90% byweight saturated hydrocarbons is provided.

The addition of a base stock selected from the group consisting of (i)an ester base stock wherein the ester base stock is present in an amountgreater than 10% by weight and no greater than about 45% by weight,based on the total weight of the lubricating oil composition, (ii) analkylated aromatic base stock, (iii) a base stock having an aromaticcontent of at least about 50% by weight, wherein the base stock havingan aromatic content of at least about 50% by weight is not an aromaticextract, and mixtures thereof to a trunk piston engine lubricating oilcomposition comprising a major amount of a base stock containing atleast 90% by weight saturated hydrocarbons advantageously improves theheavy fuel oil compatibility of the trunk piston engine lubricating oilcomposition. In addition, the trunk piston engine lubricating oilcompositions of the present invention exhibit less black sludgeformation than a trunk piston engine lubricating oil compositioncontaining only a base stock containing at least 90% by weight saturatedhydrocarbons.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is directed to a trunk piston engine lubricatingoil composition comprising (a) a major amount of a base stock containingat least 90% by weight saturated hydrocarbons; and (b) a base stockselected from the group consisting of (i) an ester base stock whereinthe ester base stock is present in an amount greater than 10% by weightand no greater than about 45% by weight, based on the total weight ofthe lubricating oil composition, (ii) an alkylated aromatic base stock,(iii) a base stock having an aromatic content of at least about 50% byweight, wherein the base stock having an aromatic content of at leastabout 50% by weight is not an aromatic extract, and mixtures thereof.The base stock containing at least 90% by weight saturated hydrocarbonsis present in a major amount, e.g., an amount greater than 50% byweight, based on the total weight of the composition. In one embodiment,the base stock containing at least 90% by weight saturated hydrocarbonsis present in an amount of greater than 50% by weight, based on thetotal weight of the composition. In another embodiment, the base stockcontaining at least 90% by weight saturated hydrocarbons is present inan amount greater than about 70% by weight, based on the total weight ofthe composition. In yet another embodiment, the base stock containing atleast 90% by weight saturated hydrocarbons is present in an amount ofgreater than 50% by weight to about 95% by weight, based on the totalweight of the composition. In still yet another embodiment, the basestock containing at least 90% by weight saturated hydrocarbons ispresent in an amount of from about 70% by weight to about 95% by weight,based on the total weight of the composition.

The base stock containing at least 90% by weight saturated hydrocarbonsmay contain one or more Group II base oils and/or one or more Group IIIbase oils and/or a base stock derived from a Fischer-Tropschsynthesized, waxy, paraffinic hydrocarbon material. A Group II base oiland/or Group III base oil can be any petroleum derived base oil oflubricating viscosity as defined in API Publication 1509, 14th Edition,Addendum I, December 1998. API guidelines define a base stock as alubricant component that may be manufactured using a variety ofdifferent processes.

Group II base oils generally refer to a petroleum derived lubricatingbase oil having a total sulfur content equal to or less than 300 partsper million (ppm) (as determined by ASTM D 2622, ASTM D 4294, ASTM D4927 or ASTM D 3120), a saturates content equal to or greater than 90weight percent (as determined by ASTM D 2007), and a viscosity index(VI) of between 80 and 120 (as determined by ASTM D 2270).

Group III base oils generally have less than 300 ppm sulfur, a saturatescontent greater than 90 weight percent, and a VI of 120 or greater. Inone embodiment, the base stock contains at least about 95% by weightsaturated hydrocarbons. In another embodiment, the base stock containsat least about 99% by weight saturated hydrocarbons.

The terms “Fischer-Tropsch derived” or “FT derived” means that theproduct, fraction, or feed originates from or is produced at some stageby a Fischer-Tropsch process. The feedstock for the Fischer-Tropschprocess may come from a wide variety of hydrocarbonaceous resources,including natural gas, coal, shale oil, petroleum, municipal waste,derivatives of these, and mixtures thereof.

Slack wax can be obtained from conventional petroleum derived feedstocksby either hydrocracking or by solvent refining of the lube oil fraction.Typically, slack wax is recovered from solvent dewaxing feedstocksprepared by one of these processes. Hydrocracking is usually preferredbecause hydrocracking will also reduce the nitrogen content to a lowvalue. With slack wax derived from solvent refined oils, deoiling may beused to reduce the nitrogen content. Hydrotreating of the slack wax canbe used to lower the nitrogen and sulfur content. Slack waxes posses avery high viscosity index, normally in the range of from about 140 to200, depending on the oil content and the starting material from whichthe slack wax was prepared. Therefore, slack waxes are suitable for thepreparation of a Fischer-Tropsch derived base stock having a very highviscosity index.

The waxy feed useful herein generally has less than about 25 ppm totalcombined nitrogen and sulfur. Nitrogen is measured by melting the waxyfeed prior to oxidative combustion and chemiluminescence detection byASTM D 4629-96. The test method is further described in U.S. Pat. No.6,503,956, the contents of which are incorporated by reference herein.Sulfur is measured by melting the waxy feed prior to ultravioletfluorescence by ASTM D 5453-00. The test method is further described inU.S. Pat. No. 6,503,956, the contents of which are incorporated byreference herein.

Waxy feeds useful in this invention are expected to be plentiful andrelatively cost competitive in the near future as large-scaleFischer-Tropsch synthesis processes come into production. Syncrudeprepared from the Fischer-Tropsch process comprises a mixture of varioussolid, liquid, and gaseous hydrocarbons. Those Fischer-Tropsch productswhich boil within the range of lubricating base oil contain a highproportion of wax which makes them ideal candidates for processing intolubricating base oil. Accordingly, Fischer-Tropsch wax represents anexcellent feed for preparing high quality lubricating base oilsaccording to the process of the invention. Fischer-Tropsch wax isnormally solid at room temperature and, consequently, displays poor lowtemperature properties, such as pour point and cloud point. However,following hydroisomerization of the wax, Fischer-Tropsch derivedlubricating base oils having excellent low temperature properties may beprepared. A general description of suitable hydroisomerization dewaxingprocesses may be found in U.S. Pat. Nos. 5,135,638 and 5,282,958; andU.S. Patent Application Publication No. 20050133409, the contents ofeach of which are incorporated by reference herein.

The hydroisomerization is achieved by contacting the waxy feed with ahydroisomerization catalyst in an isomerization zone underhydroisomerizing conditions. The hydroisomerization catalyst preferablycomprises a shape selective intermediate pore size molecular sieve, anoble metal hydrogenation component, and a refractory oxide support. Theshape selective intermediate pore size molecular sieve is preferablyselected from the group consisting of SAPO-11, SAPO-31, SAPO-41, SM-3,ZSM-22, ZSM-23, ZSM-35, ZSM-48, ZSM-57, SSZ-32, offretite, ferrierite,and mixtures thereof. SAPO-11, SM-3, SSZ-32, ZSM-23, and mixturesthereof are more preferred. Preferably the noble metal hydrogenationcomponent is platinum, palladium, or mixtures thereof.

The hydroisomerizing conditions depend on the waxy feed used, thehydroisomerization catalyst used, whether or not the catalyst issulfided, the desired yield, and the desired properties of thelubricating base oil. Preferred hydroisomerizing conditions useful inthe current invention include temperatures of 260° C. to about 413° C.(500 to about 775° F.), a total pressure of 15 to 3000 psig, and ahydrogen to feed ratio from about 0.5 to 30 MSCF/bbl, preferably fromabout 1 to about 10 MSCF/bbl, more preferably from about 4 to about 8MSCF/bbl. Generally, hydrogen will be separated from the product andrecycled to the isomerization zone.

The hydroisomerization conditions are preferably tailored to produce oneor more fractions having greater than about 5 weight percent moleculeswith monocycloparaffinic functionality, and more preferably havinggreater than about 10 weight percent molecules with monocycloparaffinicfunctionality. The fractions will preferably have a ratio of moleculeswith monocycloparaffinic functionality to molecules withmulticycloparaffinic functionality greater than about 20. The fractionswill typically have a viscosity index greater than an amount calculatedby the equation: VI=28×Ln(Kinematic Viscosity at 100° C.)+95 and a pourpoint less than 0° C. Preferably the pour point will be less than −10°C. “Ln” in the VI equation refers to the natural logarithm to the base‘e’. Viscosity index is determined by ASTM D 2270-93 (1998).

In one preferred embodiment, the base stock containing at least 90% byweight saturated hydrocarbons or at least about 95% by weight saturatedhydrocarbons or at least about 99% by weight saturated hydrocarbons isone or more Group II base oils.

Base stock (b) of the trunk piston engine lubricating oil composition isa base stock selected from the group consisting of (i) an ester basestock wherein the ester base stock is present in an amount greater than10% by weight and no greater than about 45% by weight, based on thetotal weight of the lubricating oil composition, (ii) an alkylatedaromatic base stock, and (iii) a base stock having an aromatic contentof at least about 50% by weight, wherein the base stock having anaromatic content of at least about 50% by weight is not an aromaticextract, and mixtures thereof.

Suitable organic ester base stocks include, but are not limited to,monoesters, diesters, polyol esters, and the like. The ester basestocksare generally considered Group V base stocks, which is a collection ofall base oils that do not fall into the Group I-IV base oil categories.Generally, the organic ester basestocks are derived from animal orvegetable sources. Naturally occurring organic esters are found inanimal fats such as sperm oil and lard oil, or in vegetable oils such asrapeseed and castor oil. The organic esters can be synthesized byreacting organic acids with alcohols.

Monoesters are prepared by reacting monohydric alcohols with monobasicfatty acids creating a molecule with a single ester linkage and linearor branched alkyl groups. These products are generally very low inviscosity (usually under 2 cSt at 100° C.) and exhibit extremely lowpour points and high VIs.

Diesters are prepared by reacting monohydric alcohols with dibasic acidscreating a molecule which may be linear, branched, or aromatic and withtwo ester groups. The more common diester types are adipates, azelates,sebacates, dodecanedioates, phthalates, and dimerates. In oneembodiment, the diesters include, by way of example,di(1-ethylpropyl)adipate, di(3-methylbutyl)adipate,di(1,3-methylbutyl)adipate, di(2-ethylhexyl)adipate,di(isononyl)adipate, di(isodecyl)adipate, di(undecyl)adipate,di(tridecyl)adipate, di(isotetradecyl)adipate,di(2,2,4-trimethylpentyl)adipate, di[mixed (2-ethylhexyl,isononyl)]adipate, di(1-ethylpropyl)azelate, di(3-methylbutyl)azelate,di(2-ethylbutyl)azelate, di(2-ethylhexyl)azelate, di(isooctyl)azelate,di(isononyl)azelate, di(isodecyl)azelate, di(tridecyl)azelate, di[mixed(2-ethylhexyl, isononyl)]azelate, di[mixed (2-ethylhexyl, decyl)azelate,di[mixed (2-ethylhexyl, isodecyl)]azelate, di[mixed (2-ethylhexyl,2-propylheptyl)]azelate, di(n-butyl)sebacate, di(isobutyl)sebacate,di(1-ethylpropyl)sebacate, di(1,3-methylbutyl)sebacate,di(2-methylbutyl)sebacate, di(2-ethylhexyl)sebacate,di[2-(2-ethylbutoxy)ethyl]sebacate, di(2,2,4-trimethylbenzyl)sebacate,di(isononyl)sebacate, di(isodecyl)sebacate, di(isoundecyl)sebacate,di(tridecyl)sebacate, di(isotetradecyl)sebacate, di[mixed (2-ethylhexyl,isononyl)]sebacate, di(2-ethylhexyl)glutarate, di(isoundecyl)glutarate,and di(isotetradecyl)glutarate.

Polyol esters can be prepared by esterifying one or more polyols withone or more organic acids. See, for example, U.S. Pat. No. 6,462,001,the contents of which are incorporated by reference herein. Thesynthesis of polyol esters from one or more polyols and one or moreorganic acids can be performed by methods known in the art, for example,by subjecting them to dehydrating condensation in the presence of anacid catalyst. The polyols for use in forming the polyol esters can bethose having from 2 to about 10 carbon atoms and from two to sixhydroxyl groups. One example of a polyol for use herein is a neopentylpolyol having 5 to 10 carbon atoms. The term “neopentyl polyol” as usedherein means a polyhydric alcohol having a neopentyl group. Examples ofthese polyols include, but are not limited to, 1,2-propanediol,1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol,2-ethyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 1,3-diol,(namely, neopentyl glycol), 2,2,4-trimethyl-1,3-pentanediol,2,2-diethylpropane-1,3-diol, 2,2-dibutylpropane-1,3-diol,2-methyl-2-propylpropane-1,3-diol, trimethylolpropane (TMP),pentaerythritol, dipentaerythritol and the like and mixtures thereof.

The organic acids for use in forming the polyol esters can be thosehaving from 4 to about 24 carbon atoms. Examples of organic acidsinclude, but are not limited to, butanoic acid, isobutanoic acid,pentanoic acid, isopentanoic acid, hexanoic acid, 2-ethylbutanoic acid,cyclohexanoic acid, heptanoic acid, isoheptanoic acid,methylcyclohexanoic acid, octanoic acid, dimethyl-hexanoic acid,2-ethylhexanoic acid, 2,4,4-trimethyl-pentanoic acid, isooctanoic acid,3,5,5-trimethylhexanoic acid, nonanoic acid, isononanoic acid,isodecanoic acid, isoundecanoic acid, 2-butyloctanoic acid, tridecanoicacid, tetradecanoic acid, hexadecanoic acid, heptadecanoic acid,octadecanoic acid, 2-ethylhexadecanoic acid, nonadecanoic acid,2-methyloctadecanoic acid, icosanoic acid, 2-methylicosanoic acid,3-methylnonadecanoic acid, docosanoic acid, tetradocosanoic acid,2-methyltricosanoic acid and the like and mixtures thereof.

The organic acids can also be fatty acids which are a class of compoundscontaining a long hydrocarbon chain and a terminal carboxylate group andare characterized as unsaturated or saturated depending upon whether adouble bond is present in the hydrocarbon chain. Therefore, anunsaturated fatty acid has at least one double bond in its hydrocarbonchain whereas a saturated fatty acid has no double bonds in its fattyacid chain. Examples of unsaturated fatty acids include, but are notlimited to, myristoleic acid, palmitoleic acid, oleic acid, linolenicacid and the like and mixtures thereof. Examples of saturated fattyacids include, but are not limited to, caproic acid, caprylic acid,capric acid, lauric acid, myristic acid, palmitic acid, stearic acid,arachidic acid, behenic acid, lignoceric acid and the like and mixturesthereof.

In another embodiment, the polyol ester is at least one glycerol estersuch as a C₄ to about C₇₅ fatty acid glycerol ester and preferably a C₆to about C₂₄ fatty acid glycerol ester. The glycerol esters for useherein can be glycerides derived from, for example, natural sources,i.e., those derived from natural sources such as plants or animals;synthetic oils and the like and mixtures thereof. Useful natural oilinclude, but are not limited to, coconut oil, babassu oil, palm kerneloil, palm oil, olive oil, castor oil, rape oil, corn oil, beef tallowoil, whale oil, sunflower, cottonseed oil, linseed oil, tung oil, tallowoil, lard oil, peanut oil, canola oil, soya oil, and the like andmixtures thereof. Useful synthetic oils include, but are not limited to,synthetic oils derived from the reaction of one or more carboxylic acidswith one or more glycerols, e.g., glycerol triacetate, and the like andmixtures thereof. Suitable starting oils will ordinarily containtriacylglycerols (TAGs), which contain three fatty acid chainsesterified to a glycerol moiety and can be natural or synthetic. Forexample, TAGs such as triolein, trieicosenoin, or trierucin can be usedas starting materials. TAGs are commercially available, for example,from Sigma Chemical Company (St. Louis, Mo.), or can be synthesizedusing standard techniques.

The foregoing glycerol esters can contain from about C₄ to about C₇₅ andpreferably contain about C₆ to about C₂₄ fatty acid esters, i.e.,several fatty acid moieties, the number and type varying with the sourceof the oil. The fatty acid moieties independently can be unsaturated orsaturated fatty acids. Examples of unsaturated fatty acids include, butare not limited to, myristoleic acid, palmitoleic acid, oleic acid,linolenic acid, and the like and mixtures thereof. Examples of saturatedfatty acids include, but are not limited to, caproic acid, caprylicacid, capric acid, lauric acid, myristic acid, palmitic acid, stearicacid, arachidic acid, behenic acid, lignoceric acid, and the like andmixtures thereof.

The acid moiety may be supplied in a fully esterfied compound or onewhich is less than fully esterfied, e.g., glyceryl tri-stearate,glyceryl di-laurate and glyceryl mono-oleate, respectively. As oneskilled in the art will readily appreciate, the starting material can beplant derived oils, i.e., vegetable oils. Suitable vegetable oils have amonounsaturated fatty acid content of at least about 50%, based on totalfatty acid content, and include, for example, rapeseed (Brassica),sunflower (Helianthus), soybean (Glycine max), corn (Zea mays), crambe(Crambe), and meadowfoam (Limnanthes) oil. Canola oil, which has lessthan 2% erucic acid, is a particularly useful rapeseed oil. Oils havinga monounsaturated fatty acid content of at least 70% are alsoparticularly useful. The monounsaturated fatty acid content can becomposed of, for example, oleic acid (C_(18:1)), eicosenoic acid(C_(20:1)), erucic acid (C_(22:1)), or mixtures thereof.

In one embodiment, the polyol esters can be glycerol esters of thegeneral formula (I):

wherein R¹, R² and R³ are independently aliphatic hydrocarbyl moietieshaving 4 to about 75 carbon atoms, preferably 4 to about 24 carbon atomsinclusive, and more preferably wherein at least one of R¹, R² and R³ isa saturated aliphatic hydrocarbyl moiety having 4 to about 10 carbonatoms inclusive and wherein at least one of R¹, R² and R³ is analiphatic hydrocarbyl moiety having from 11 to about 24 carbon atomsinclusive.

In another embodiment, the polyol esters are compounds of the generalformula (II):

wherein R⁴, R⁵ and R⁶ are independently aliphatic hydrocarbyl moietieshaving from 4 to about 24 carbon atoms, R⁷ is hydrogen or an aliphatichydrocarbyl moiety having 1 to 10 carbon atoms and x, y and z are thesame or different and are integers from 1 to 10. The compounds offormula (II) are known compounds and can be prepared by known proceduresand hence readily commercially available. Referring to the R⁴, R⁵ and R⁶groups, the aliphatic hydrocarbyl moieties may be independentlysaturated or unsaturated, linear (straight chain) or branched chain andpreferably have 4 to about 24 carbon atoms, more preferably 4 to about16 carbon atoms and most preferably 6 to about 10 carbon atoms. The R⁷group can be hydrogen or an aliphatic hydrocarbyl moiety such as, by wayof example, a linear or branched chain alkyl group having from 1 toabout 10 carbon atoms and preferably 1 to 6 carbon atoms, optionallycontaining an aromatic or aryl group. Examples of such polyol esters foruse herein include, but are not limited to, trimethylolpropane (TMP)esters such as, for example, TMP tri(2-ethyl hexanoate), TMPtriheptanoate, TMP tricaprylate, TMP tricaprate, TMP tri(isononanoate)and the like.

In one embodiment, an ester base stock for use in the trunk pistonengine lubricating oil compositions of the present invention is an esterbase stock having a kinematic viscosity of about 2 to about 10 cSt at100° C. In another embodiment, an ester base stock for use in the trunkpiston engine lubricating oil compositions of the present invention isan ester base stock having a kinematic viscosity of greater than about10 to about 100 cSt at 100° C.

In one embodiment, an ester base stock for use in the trunk pistonengine lubricating oil compositions of the present invention isPriolube® 3970, a polyol ester which is an ester of a neopentyl polyol,suitably trimethylolpropane, with at least one aliphatic, saturatedmonocarboxylic acid having 6 to 12 carbon atoms and having a kinematicviscosity at 100° C. of 4.4 cSt.

In another embodiment, the ester base stock will be present in the trunkpiston engine lubricating oil compositions of the present invention inan amount of from about 20% by weight and no greater than about 40% byweight, based on the total weight of the trunk piston engine lubricatingoil composition.

Alkylated aromatic base stocks for use in the trunk piston enginelubricating oil composition of the present invention can bemonoalkylated aromatic base stocks, dialkylated aromatic base stocks,tri alkylated aromatic base stocks and the like. The alkylated aromaticbase stocks are generally considered Group V base stocks. The alkylatedmoiety can be, for example, any linear or branched alkyl groups of aboutC₆ to C₃₀ alkyl, such as those derived from a C₆ to C₃₀ alpha olefinalkylating agent. Suitable aromatic group(s) can be of any molecularstructure having aromatic character such as at least one six memberedaromatic ring, optionally having any number of such six-membered ringsfused together or connected by bonds or linking structures such asbenzene rings, diphenyl rings. For example, the aromatic groups can havefrom 1 to about 10 such substituted or unsubstituted aromatic rings. Ifdesired, when more than one cyclic containing group such as the aromaticgroups are employed, the cyclic containing groups can be linked togetherwith the same or different linking group, e.g., a C₁ to C₂₀ alkylene orhaloalkylene group optionally containing ether or ester linkages.Suitable fused and/or polyfused aromatic groups include, but are notlimited to, anthracene, phenanthrene, pyrene, indene, acenaphthylene,benzanthrene, chrysene, triphenylene, and naphthalene. In one preferredembodiment, the aromatic group is naphthalene.

The alkylated aromatic base stocks are either commercially availablefrom such sources as King Industries under the KR Series, e.g., NA-LUBE®KR-007, and the like, or can be prepared by any method known in the art.See, for example, Synthetics, Mineral Oils, and Bio-Based Lubricants,Chemistry and Technology, Leslie R. Rudnick (editor), Taylor & Francis,7, pp. 139-146 (2006), the contents of which are incorporated byreference herein. NA-LUBE® is a registered trademark of King IndustriesSpecialty Chemicals. For example, alkylated aromatic base stocks such asalkylated naphthalenes can be produced from the alkylation of aromaticswith an olefin, alcohol, alkylhalide, or other alkylating agents knownto those of skill in the art in the presence of a catalyst. Suitablecatalysts include any of Lewis acid or super acid catalysts known in theart. Suitable Lewis acids include boron trifluoride, iron trichloride,tin tetrachloride, zinc dichloride, and antimony pentafluoride. Acidicclays, silica, or alumina are also suitable. See, for example, U.S. Pat.Nos. 4,604,491 and 4,764,794. Suitable super acid catalysts includetrifluoromethane sulfonic acid, hydrofluoric acid ortrifluoromethylbenzene sulfonic acid. Other suitable catalysts includeacidic zeolite catalysts, such as Zeolite Beta, Zeolite Y, ZSM-5,ZSM-35, and USY.

In one embodiment, the alkylated aromatic base stock will be present inthe trunk piston engine lubricating oil compositions of the presentinvention in an amount of from about 1% by weight to about 45% byweight, based on the total weight of the trunk piston engine lubricatingoil composition. In another embodiment, the alkylated aromatic basestock will be present in the trunk piston engine lubricating oilcompositions of the present invention in an amount of from about 5% byweight to about 40% by weight, based on the total weight of thelubricating oil composition. In another embodiment, the alkylatedaromatic base stock will be present in the trunk piston enginelubricating oil compositions of the present invention in an amount offrom about 25% by weight to about 35% by weight, based on the totalweight of the lubricating oil composition.

The base stock having an aromatic content of at least about 50% byweight is known in the art and includes those highly aromatic basestocks which are recovered from the refining of petroleum-derivedfeedstocks, such as by fluid catalytic cracking (FCC and the related TCCprocess), coking, pyrolysis, and the like. These base stocks aregenerally considered Group V base stocks. In one embodiment, a basestock having an aromatic content of at least about 50% by weight for usein preparing the trunk piston engine lubricating oil compositions of thepresent invention is one or more of FCC light cycle oils, FCC mediumcycle oils, FCC heavy cycle oils and mixtures thereof, which are derivedfrom a catalytic cracking refinery operation such as fluidized catalyticcracking refinery operations. A “light cycle oil” refers to hydrocarbonshaving a boiling range distribution between about 302° F. (150° C.) andabout 752° F. (400° C.) that are produced from a fluidized catalyticcracking system. Light cycle oil content is determined by ASTM MethodD5307. A “medium cycle oil” refers to hydrocarbons having a boilingrange distribution between about 270° F. (132° C.) and about 900° F.(482° C.) that are produced from fluidized catalytic cracking system.Heavy cycle oil content is determined by ASTM Method D5307. A “heavycycle oil” refers to hydrocarbons having a boiling range distributionbetween about 320° F. (160° C.) and about 1112° F. (600° C.) that areproduced from fluidized catalytic cracking system. Heavy cycle oilcontent is determined by ASTM Method D5307.

In general, a FCC medium cycle oil can be a mixture of mono-, di andpolyaromatics, e.g., a mixture of from about 5% by weight to about 15%by weight monoaromatics, from about % by weight to about 50% by weightdiaromatics and from about 20% by weight to about 35% by weightpolyaromatics. Examples of a FCC medium cycle oil for use herein includea normal FCC medium cycle oil, heavy FCC medium cycle oil and the likeand mixtures thereof.

In one embodiment, the base stock having an aromatic content of at leastabout 50% by weight will be base stock having an aromatic content of atleast about 60 percent by weight of aromatics.

In one embodiment, the base stock having an aromatic content of at leastabout 50% by weight will be present in the trunk piston enginelubricating oil compositions of the present invention in an amount offrom about 1% by weight to about 45% by weight, based on the totalweight of the lubricating oil composition. In another embodiment, thebase stock having an aromatic content of at least about 50% by weightwill be present in the trunk piston engine lubricating oil compositionsof the present invention in an amount of from about 5% by weight toabout 40% by weight, based on the total weight of the lubricating oilcomposition. In another embodiment, the base stock having an aromaticcontent of at least about 50% by weight will be present in the trunkpiston engine lubricating oil compositions of the present invention inan amount of from about 25% by weight to about 35% by weight, based onthe total weight of the trunk piston engine lubricating oil composition.

The base stock having an aromatic content of at least about 50% byweight is not an aromatic extract. In general, an aromatic extract is anextract that can be made by the treatment of at least one refineryprocess stream in a solvent extraction process. Solvent extractionprocesses include contacting the at least one refinery process streamwith a solvent such as furfural, n-methylpyrrolidone, sulphur dioxide,Duo-Sol™ or phenol to selectively extract from the refinery stream,aromatic heterocyclic materials and to form a solution of thesematerials in the solvent. The solvent is then recovered from thesolution for recycle to the extraction process; the resultant productbeing the aromatic extract.

The manufacture of aromatic extracts is known in the art and isdescribed, for example, in “Lubricant base oil and wax processing” A.Sequeira, pages 81-118, pub. Marcel Dekker Inc. New York, 1994.

The aromatic extract may be a residual aromatic extract, which may bemade by treatment in an extraction process, of solvent deasphaltedvacuum residue (also known as DAO) made using Duo-Sol™, propane, butaneor mixtures thereof as the solvent for the deasphalting.

The aromatic extract may be a distillate aromatic extract (DAE) which isan aromatic extract made by treatment in an extraction process, of adistillate stream from a vacuum distillation process. The distillatearomatic extract can be a treated distillate aromatic extract which is adistillate aromatic extract which has been subjected to at least onefurther treatment, e,g., hydrotreatment, hydrogenation,hydrodesulphurization, clay treatment, acid treatment and furthersolvent extraction.

The aromatic extract may have an aromatics content of 60 to 85 weight %,which may be measured by ASTM D 2007.

The distillate aromatic extract may have a boiling point in the range250 to 680° C., which may be measured according to ASTM D2887. Thedistillate aromatic extract may have a kinematic viscosity at 40° C. inthe range 5 to 18000 mm²/s, which may be measured according to ASTM D445. The distillate aromatic extract may have a kinematic viscosity at100° C. in the range 3 to 60 mm²/s, which may be measured according toASTM D 445. The distillate aromatic extract may have an averagemolecular mass in the range 300 to 580, which may be measured accordingto ASTM D 2887. The distillate aromatic extract may have a carbon numberrange in the range C₁₅ to C₅₄, which may be measured according to ASTMD2887. The distillate aromatic extract may have an aromatic content inthe range 65 to 85 weight %, which may be measured according to ASTM D2007.

The residual aromatic extract may have a boiling point of greater than380° C., which may be measured according to ASTM D 2887. The residualaromatic extract may have a kinematic viscosity at 40° C. of great than4000 mm²/s, which may be measured according to ASTM D 445.

The residual aromatic extract may have a kinematic viscosity at 100° C.in the range 60-330 mm²/s, which may be measured according to ASTM D445. The residual aromatic extract may have an average molecular mass ofgreater than 400, which may be measured according to ASTM D 2887. Theresidual aromatic extract may have a carbon number range of greater thanC₂₅, which may be measured according to ASTM D 2887. The residualaromatic extract may have an aromatic content in the range 60 to 85weight %, which may be measured according to ASTM D 2007.

The trunk piston engine lubricating oil compositions of the presentinvention can have any total base number (TBN) that is suitable for usein trunk piston engines. The term “total base number” or “TBN” refers tothe amount of base equivalent to milligrams of KOH in 1 gram of sample.Thus, higher TBN numbers reflect more alkaline products and therefore agreater alkalinity reserve. The TBN of the trunk piston enginelubricating oil compositions can be measured by any suitable method,such as by ASTM D2896. In general, the trunk piston engine lubricatingoil compositions can have a TBN of at least about 12. In one embodiment,the trunk piston engine lubricating oil compositions can have a TBN offrom about 20 to about 60. In another embodiment, the trunk pistonengine lubricating oil compositions can have a TBN of from about 30 toabout 50.

The trunk piston engine lubricating oil compositions of the presentinvention can have any viscosity that is suitable for use in a trunkpiston engine. Generally, the trunk piston engine lubricating oilcomposition can have a viscosity ranging from about 5 to about 25centistokes (cSt) at 100° C. and preferably from about 10 to about 20cSt at 100° C. The viscosity of the trunk piston engine lubricating oilcomposition can be measured by any suitable method, e.g., ASTM D2270.

The trunk piston engine lubricating oil compositions of the presentinvention can be prepared by any method known to a person of ordinaryskill in the art for making trunk piston engine lubricating oils. Theingredients can be added in any order and in any manner. Any suitablemixing or dispersing equipment may be used for blending, mixing orsolubilizing the ingredients. The blending, mixing or solubilizing maybe carried out with a blender, an agitator, a disperser, a mixer (e.g.,planetary mixers and double planetary mixers), a homogenizer (e.g., aGaulin homogenizer or Rannie homogenizer), a mill (e.g., colloid mill,ball mill or sand mill) or any other mixing or dispersing equipmentknown in the art.

In one embodiment, the trunk piston engine lubricating oil compositionsof the present invention are substantially free of a Group I base oil.The term “substantially free” as used herein shall be understood to meanrelatively little to no amount of any Group I base oil, e.g., an amountless than about 5% by weight, preferably less than 1% by weight, andmost preferably less than about 0.1% by weight, based on the totalweight of the trunk piston engine lubricating oil composition. The term“Group I base oil” as used herein refers to a petroleum derivedlubricating base oil having a saturates content of less than 90 wt. %(as determined by ASTM D 2007) and/or a total sulfur content of greaterthan 300 ppm (as determined by ASTM D 2622, ASTM D 4294, ASTM D 4297 orASTM D 3120) and has a viscosity index (VI) of greater than or equal to80 and less than 120 (as determined by ASTM D 2270).

The trunk piston engine lubricating oil compositions of the presentinvention may also contain conventional trunk piston engine lubricatingoil composition additives for imparting auxiliary functions to give afinished trunk piston engine lubricating oil composition in which theseadditives are dispersed or dissolved. For example, the trunk pistonengine lubricating oil compositions can be blended with antioxidants,ashless dispersants, anti-wear agents, detergents such as metaldetergents, rust inhibitors, dehazing agents, demulsifying agents, metaldeactivating agents, friction modifiers, pour point depressants,antifoaming agents, co-solvents, package compatibilisers,corrosion-inhibitors, dyes, extreme pressure agents and the like andmixtures thereof. A variety of the additives are known and commerciallyavailable. These additives, or their analogous compounds, can beemployed for the preparation of the trunk piston engine lubricating oilcompositions of the invention by the usual blending procedures.

Representative examples of antioxidants include, but are not limited to,aminic types, e.g., diphenylamine, phenyl-alpha-napthyl-amine,N,N-di(alkylphenyl)amines; and alkylated phenylene-diamines; phenolicssuch as, for example, BHT, sterically hindered alkyl phenols such as2,6-di-tert-butylphenol, 2,6-di-tert-butyl-p-cresol and2,6-di-tert-butyl-4-(2-octyl-3-propanoic) phenol; and mixtures thereof.

Representative examples of ashless dispersants include, but are notlimited to, amines, alcohols, amides, or ester polar moieties attachedto the polymer backbones via bridging groups. An ashless dispersant ofthe present invention may be, for example, selected from oil solublesalts, esters, amino-esters, amides, imides, and oxazolines of longchain hydrocarbon substituted mono and dicarboxylic acids or theiranhydrides; thiocarboxylate derivatives of long chain hydrocarbons, longchain aliphatic hydrocarbons having a polyamine attached directlythereto; and Mannich condensation products formed by condensing a longchain substituted phenol with formaldehyde and polyalkylene polyamine.

Carboxylic dispersants are reaction products of carboxylic acylatingagents (acids, anhydrides, esters, etc.) comprising at least about 34and preferably at least about 54 carbon atoms with nitrogen containingcompounds (such as amines), organic hydroxy compounds (such as aliphaticcompounds including monohydric and polyhydric alcohols, or aromaticcompounds including phenols and naphthols), and/or basic inorganicmaterials. These reaction products include imides, amides, and esters.

Succinimide dispersants are a type of carboxylic dispersant. They areproduced by reacting hydrocarbyl-substituted succinic acylating agentwith organic hydroxy compounds, or with amines comprising at least onehydrogen atom attached to a nitrogen atom, or with a mixture of thehydroxy compounds and amines. The term “succinic acylating agent” refersto a hydrocarbon-substituted succinic acid or a succinic acid-producingcompound, the latter encompasses the acid itself. Such materialstypically include hydrocarbyl-substituted succinic acids, anhydrides,esters (including half esters) and halides.

Succinic-based dispersants have a wide variety of chemical structures.One class of succinic-based dispersants may be represented by theformula:

wherein each R¹ is independently a hydrocarbyl group, such as apolyolefin-derived group. Typically the hydrocarbyl group is an alkylgroup, such as a polyisobutyl group. Alternatively expressed, the R¹groups can contain about 40 to about 500 carbon atoms, and these atomsmay be present in aliphatic forms. R² is an alkylene group, commonly anethylene (C₂H₄) group. Examples of succinimide dispersants include thosedescribed in, for example, U.S. Pat. Nos. 3,172,892, 4,234,435 and6,165,235.

The polyalkenes from which the substituent groups are derived aretypically homopolymers and interpolymers of polymerizable olefinmonomers of 2 to about 16 carbon atoms, and usually 2 to 6 carbon atoms.The amines which are reacted with the succinic acylating agents to formthe carboxylic dispersant composition can be monoamines or polyamines.

Succinimide dispersants are referred to as such since they normallycontain nitrogen largely in the form of imide functionality, althoughthe amide functionality may be in the form of amine salts, amides,imidazolines as well as mixtures thereof. To prepare a succinimidedispersant, one or more succinic acid-producing compounds and one ormore amines are heated and typically water is removed, optionally in thepresence of a substantially inert organic liquid solvent/diluent. Thereaction temperature can range from about 80° C. up to the decompositiontemperature of the mixture or the product, which typically falls betweenabout 100° C. to about 300° C. Additional details and examples ofprocedures for preparing the succinimide dispersants of the presentinvention include those described in, for example, U.S. Pat. Nos.3,172,892, 3,219,666, 3,272,746, 4,234,435, 6,165,235 and 6,440,905.

Suitable ashless dispersants may also include amine dispersants, whichare reaction products of relatively high molecular weight aliphatichalides and amines, preferably polyalkylene polyamines. Examples of suchamine dispersants include those described in, for example, U.S. Pat.Nos. 3,275,554, 3,438,757, 3,454,555 and 3,565,804.

Suitable ashless dispersants may further include “Mannich dispersants,”which are reaction products of alkyl phenols in which the alkyl groupcontains at least about 30 carbon atoms with aldehydes (especiallyformaldehyde) and amines (especially polyalkylene polyamines). Examplesof such dispersants include those described in, for example, U.S. PatentNos. 3,036,003, 3,586,629. 3,591,598 and 3,980,569.

Suitable ashless dispersants may also be post-treated ashlessdispersants such as post-treated succinimides, e.g., post-treatmentprocesses involving borate or ethylene carbonate as disclosed in, forexample, U.S. Pat. Nos. 4,612,132 and 4,746,446; and the like as well asother post-treatment processes. The carbonate-treated alkenylsuccinimide is a polybutene succinimide derived from polybutenes havinga molecular weight of about 450 to about 3000, preferably from about 900to about 2500, more preferably from about 1300 to about 2400, and mostpreferably from about 2000 to about 2400, as well as mixtures of thesemolecular weights. Preferably, it is prepared by reacting, underreactive conditions, a mixture of a polybutene succinic acid derivative,an unsaturated acidic reagent copolymer of an unsaturated acidic reagentand an olefin, and a polyamine, such as disclosed in U.S. Pat. No.5,716,912, the contents of which are incorporated by reference herein.

Suitable ashless dispersants may also be polymeric, which areinterpolymers of oil-solubilizing monomers such as decyl methacrylate,vinyl decyl ether and high molecular weight olefins with monomerscontaining polar substitutes. Examples of polymeric dispersants includethose described in, for example, U.S. Pat. Nos. 3,329,658; 3,449,250 and3,666,730.

In one preferred embodiment of the present invention, an ashlessdispersant for use in the lubricating oil composition is abis-succinimide derived from a polyisobutenyl group having a numberaverage molecular weight of about 700 to about 2300. The dispersant(s)for use in the lubricating oil compositions of the present invention arepreferably non-polymeric (e.g., are mono- or bis-succinimides).

Generally, the one or more ashless dispersants are present in thelubricating oil composition in an amount ranging from about 0.01% byweight to about 10% by weight, based on the total weight of thelubricating oil composition.

Representative examples of antiwear agents include, but are not limitedto, zinc dialkyldithiophosphates and zinc diaryldithiophosphates, e.g.,those described in an article by Born et al. entitled “Relationshipbetween Chemical Structure and Effectiveness of Some Metallic Dialkyl-and Diaryl-dithiophosphates in Different Lubricated Mechanisms”,appearing in Lubrication Science 4-2 Jan. 1992, see for example pages97-100; aryl phosphates and phosphites, sulfur-containing esters,phosphosulfur compounds, metal or ash-free dithiocarbamates, xanthates,alkyl sulfides and the like and mixtures thereof.

Representative examples of metal detergents include sulphonates,alkylphenates, sulfurized alkyl phenates, carboxylates, salicylates,phosphonates, and phosphinates. Commercial products are generallyreferred to as neutral or overbased. Overbased metal detergents aregenerally produced by carbonating a mixture of hydrocarbons, detergentacid, for example: sulfonic acid, alkylphenol, carboxylate etc., metaloxide or hydroxides (for example calcium oxide or calcium hydroxide) andpromoters such as xylene, methanol and water. For example, for preparingan overbased calcium sulfonate, in carbonation, the calcium oxide orhydroxide reacts with the gaseous carbon dioxide to form calciumcarbonate. The sulfonic acid is neutralized with an excess of CaO orCa(OH)₂, to form the sulfonate.

Metal-containing or ash-forming detergents function as both detergentsto reduce or remove deposits and as acid neutralizers or rustinhibitors, thereby reducing wear and corrosion and extending enginelife. Detergents generally comprise a polar head with a long hydrophobictail. The polar head comprises a metal salt of an acidic organiccompound. The salts may contain a substantially stoichiometric amount ofthe metal in which case they are usually described as normal or neutralsalts, and would typically have a total base number or TBN (as can bemeasured by ASTM D2896) of from 0 to about 80. A large amount of a metalbase may be incorporated by reacting excess metal compound (e.g., anoxide or hydroxide) with an acidic gas (e.g., carbon dioxide). Theresulting overbased detergent comprises neutralized detergent as theouter layer of a metal base (e.g., carbonate) micelle. Such overbaseddetergents may have a TBN of about 150 or greater, and typically willhave a TBN of from about 250 to about 450 or more.

Detergents that may be used include oil-soluble neutral and overbasedsulfonates, phenates, sulfurized phenates, thiophosphonates,salicylates, and naphthenates and other oil-soluble carboxylates of ametal, particularly the alkali or alkaline earth metals, e.g., barium,sodium, potassium, lithium, calcium, and magnesium. The most commonlyused metals are calcium and magnesium, which may both be present indetergents used in a lubricant, and mixtures of calcium and/or magnesiumwith sodium. Particularly convenient metal detergents are neutral andoverbased calcium sulfonates having TBN of from about 20 to about 450,neutral and overbased calcium phenates and sulfurized phenates havingTBN of from about 50 to about and neutral and overbased magnesium orcalcium salicylates having a TBN of from about 20 to about 450. Mixturesof detergents, whether overbased or neutral or both, may be used.

In one embodiment, the detergent can be one or more alkali or alkalineearth metal salts of an alkyl-substituted hydroxyaromatic carboxylicacid. Suitable hydroxyaromatic compounds include mononuclear monohydroxyand polyhydroxy aromatic hydrocarbons having 1 to 4, and preferably 1 to3, hydroxyl groups. Suitable hydroxyaromatic compounds include phenol,catechol, resorcinol, hydroquinone, pyrogallol, cresol, and the like.The preferred hydroxyaromatic compound is phenol.

The alkyl substituted moiety of the alkali or alkaline earth metal saltof an alkyl-substituted hydroxyaromatic carboxylic acid is derived froman alpha olefin having from about 10 to about 80 carbon atoms. Theolefins employed may be linear, isomerized linear, branched or partiallybranched linear. The olefin may be a mixture of linear olefins, amixture of isomerized linear olefins, a mixture of branched olefins, amixture of partially branched linear or a mixture of any of theforegoing.

In one embodiment, the mixture of linear olefins that may be used is amixture of normal alpha olefins selected from olefins having from about12 to about 30 carbon atoms per molecule. In one embodiment, the normalalpha olefins are isomerized using at least one of a solid or liquidcatalyst.

In another embodiment, the olefins are a branched olefinic propyleneoligomer or mixture thereof having from about 20 to about 80 carbonatoms, i.e., branched chain olefins derived from the polymerization ofpropylene. The olefins may also be substituted with other functionalgroups, such as hydroxy groups, carboxylic acid groups, heteroatoms, andthe like. In one embodiment, the branched olefinic propylene oligomer ormixtures thereof have from about 20 to about 60 carbon atoms. In oneembodiment, the branched olefinic propylene oligomer or mixtures thereofhave from about 20 to about 40 carbon atoms.

In one embodiment, at least about 75 mole % (e.g., at least about 80mole %, at least about 85 mole %, at least about 90 mole %, at leastabout 95 mole %, or at least about 99 mole %) of the alkyl groupscontained within the alkali or alkaline earth metal salt of analkyl-substituted hydroxyaromatic carboxylic acid such as the alkylgroups of an alkaline earth metal salt of an alkyl-substitutedhydroxybenzoic acid detergent are a C₂₀ or higher. In anotherembodiment, the alkali or alkaline earth metal salt of analkyl-substituted hydroxyaromatic carboxylic acid is an alkali oralkaline earth metal salt of an alkyl-substituted hydroxybenzoic acidthat is derived from an alkyl-substituted hydroxybenzoic acid in whichthe alkyl groups are the residue of normal alpha-olefins containing atleast 75 mole % C₂₀ or higher normal alpha-olefins.

In another embodiment, at least about 50 mole % (e.g., at least about 60mole %, at least about 70 mole %, at least about 80 mole %, at leastabout 85 mole %, at least about 90 mole %, at least about 95 mole %, orat least about 99 mole %) of the alkyl groups contained within thealkali or alkaline earth metal salt of an alkyl-substitutedhydroxyaromatic carboxylic acid such as the alkyl groups of an alkali oralkaline earth metal salt of an alkyl-substituted hydroxybenzoic acidare about C₁₄ to about C₁₈.

The resulting alkali or alkaline earth metal salt of analkyl-substituted hydroxyaromatic carboxylic acid will be a mixture ofortho and para isomers. In one embodiment, the product will containabout 1 to 99% ortho isomer and 99 to 1% para isomer. In anotherembodiment, the product will contain about 5 to 70% ortho and 95 to 30%para isomer.

The alkali or alkaline earth metal salts of an alkyl-substitutedhydroxyaromatic carboxylic acid can be neutral or overbased. Generally,an overbased alkali or alkaline earth metal salt of an alkyl-substitutedhydroxyaromatic carboxylic acid is one in which the BN of the alkali oralkaline earth metal salts of an alkyl-substituted hydroxyaromaticcarboxylic acid has been increased by a process such as the addition ofa base source (e.g., lime) and an acidic overbasing compound (e.g.,carbon dioxide).

Overbased salts may be low overbased, e.g., an overbased salt having aBN below about 100. In one embodiment, the BN of a low overbased saltmay be from about 5 to about 50. In another embodiment, the BN of a lowoverbased salt may be from about 10 to about 30. In yet anotherembodiment, the BN of a low overbased salt may be from about 15 to about20.

Overbased detergents may be medium overbased, e.g., an overbased salthaving a BN from about 100 to about 250. In one embodiment, the BN of amedium overbased salt may be from about 100 to about 200. In anotherembodiment, the BN of a medium overbased salt may be from about 125 toabout 175.

Overbased detergents may be high overbased, e.g., an overbased salthaving a BN above about 250. In one embodiment, the BN of a highoverbased salt may be from about 250 to about 450.

Sulfonates may be prepared from sulfonic acids which are typicallyobtained by the sulfonation of alkyl substituted aromatic hydrocarbonssuch as those obtained from the fractionation of petroleum or by thealkylation of aromatic hydrocarbons. Examples included those obtained byalkylating benzene, toluene, xylene, naphthalene, diphenyl or theirhalogen derivatives. The alkylation may be carried out in the presenceof a catalyst with alkylating agents having from about 3 to more than 70carbon atoms. The alkaryl sulfonates usually contain from about 9 toabout 80 or more carbon atoms, preferably from about 16 to about 60carbon atoms per alkyl substituted aromatic moiety.

The oil soluble sulfonates or alkaryl sulfonic acids may be neutralizedwith oxides, hydroxides, alkoxides, carbonates, carboxylate, sulfides,hydrosulfides, nitrates, borates and ethers of the metal. The amount ofmetal compound is chosen having regard to the desired TBN of the finalproduct but typically ranges from about 100 to about 220 wt. %(preferably at least about 125 wt. %) of that stoichiometricallyrequired.

Metal salts of phenols and sulfurized phenols are prepared by reactionwith an appropriate metal compound such as an oxide or hydroxide andneutral or overbased products may be obtained by methods well known inthe art. Sulfurized phenols may be prepared by reacting a phenol withsulfur or a sulfur containing compound such as hydrogen sulfide, sulfurmonohalide or sulfur dihalide, to form products which are generallymixtures of compounds in which 2 or more phenols are bridged by sulfurcontaining bridges.

Generally, the detergents can be present in the trunk piston enginelubricating oil compositions in amount of about 1% by weight to about15% by weight, based on the total weight of the trunk piston enginelubricating oil composition.

Representative examples of rust inhibitors include, but are not limitedto, nonionic polyoxyalkylene agents, e.g., polyoxyethylene lauryl ether,polyoxyethylene higher alcohol ether, polyoxyethylene nonylphenyl ether,polyoxyethylene octylphenyl ether, polyoxyethylene octyl stearyl ether,polyoxyethylene oleyl ether, polyoxyethylene sorbitol monostearate,polyoxyethylene sorbitol monooleate, and polyethylene glycol monooleate;stearic acid and other fatty acids; dicarboxylic acids; metal soaps;fatty acid amine salts; metal salts of heavy sulfonic acid; partialcarboxylic acid ester of polyhydric alcohol; phosphoric esters;(short-chain) alkenyl succinic acids; partial esters thereof andnitrogen-containing derivatives thereof synthetic alkarylsulfonates,e.g., metal dinonylnaphthalene sulfonates; and the like and mixturesthereof.

Representative examples of friction modifiers include, but are notlimited to, alkoxylated fatty amines; borated fatty epoxides; fattyphosphites, fatty epoxides, fatty amines, borated alkoxylated fattyamines, metal salts of fatty acids, fatty acid amides, glycerol esters,borated glycerol esters; and fatty imidazolines as disclosed in U.S.Pat. No. 6,372,696, the contents of which are incorporated by referenceherein; friction modifiers obtained from a reaction product of a C₄ toC₇₅, preferably a C₆ to C₂₄, and most preferably a C₆ to C₂₀, fatty acidester and a nitrogen-containing compound selected from the groupconsisting of ammonia, and an alkanolamine and the like and mixturesthereof.

Representative examples of antifoaming agents include, but are notlimited to, polymers of alkyl methacrylate; polymers of dimethylsiliconeand the like and mixtures thereof.

Representative examples of a pour point depressant include, but are notlimited to, polymethacrylates, alkyl acrylate polymers, alkylmethacrylate polymers, di(tetra-paraffin phenol)phthalate, condensatesof tetra-paraffin phenol, condensates of a chlorinated paraffin withnaphthalene and mixtures thereof. In one embodiment, a pour pointdepressant comprises an ethylene-vinyl acetate copolymer, a condensateof chlorinated paraffin and phenol, polyalkyl styrene and the like andmixtures thereof. The amount of the pour point depressant may vary fromabout 0.01% by weight to about 10% by weight.

Representative examples of a demulsifier include, but are not limitedto, anionic surfactants (e.g., alkyl-naphthalene sulfonates, alkylbenzene sulfonates and the like), nonionic alkoxylated alkylphenolresins, polymers of alkylene oxides (e.g., polyethylene oxide,polypropylene oxide, block copolymers of ethylene oxide, propylene oxideand the like), esters of oil soluble acids, polyoxyethylene sorbitanester and the like and mixtures thereof. The amount of the demulsifiermay vary from about 0.01% by weight to about 10% by weight.

Representative examples of a corrosion inhibitor include, but are notlimited to, half esters or amides of dodecylsuccinic acid, phosphateesters, thiophosphates, alkyl imidazolines, sarcosines and the like andmixtures thereof. The amount of the corrosion inhibitor may vary fromabout 0.01% by weight to about 5% by weight.

Representative examples of an extreme pressure agent include, but arenot limited to, sulfurized animal or vegetable fats or oils, sulfurizedanimal or vegetable fatty acid esters, fully or partially esterifiedesters of trivalent or pentavalent acids of phosphorus, sulfurizedolefins, dihydrocarbyl polysulfides, sulfurized Diels-Alder adducts,sulfurized dicyclopentadiene, sulfurized or co-sulfurized mixtures offatty acid esters and monounsaturated olefins, co-sulfurized blends offatty acid, fatty acid ester and alpha-olefin, functionally-substituteddihydrocarbyl polysulfides, thia-aldehydes, thia-ketones, epithiocompounds, sulfur-containing acetal derivatives, co-sulfurized blends ofterpene and acyclic olefins, and polysulfide olefin products, aminesalts of phosphoric acid esters or thiophosphoric acid esters and thelike and mixtures thereof. The amount of the extreme pressure agent mayvary from about 0.01% by weight to about 5% by weight.

Each of the foregoing additives, when used, is used at a functionallyeffective amount to impart the desired properties to the lubricant.Thus, for example, if an additive is a friction modifier, a functionallyeffective amount of this friction modifier would be an amount sufficientto impart the desired friction modifying characteristics to thelubricant. Generally, the concentration of each of these additives, whenused, may range, unless otherwise specified, from about 0.001% to about20% by weight, and in one embodiment about 0.01% to about 10% by weightbased on the total weight of the lubricating oil composition.

If desired, the trunk piston engine lubricating oil additives may beprovided as an additive package or concentrate in which the additivesare incorporated into a substantially inert, normally liquid organicdiluent such as, for example, mineral oil, naphtha, benzene, toluene orxylene to form an additive concentrate. These concentrates usuallycontain from about 20% to about 80% by weight of such diluent. Typicallya neutral oil having a viscosity of about 4 to about 8.5 cSt at 100° C.and preferably about 4 to about 6 cSt at 100° C. will be used as thediluent, though synthetic oils, as well as other organic liquids whichare compatible with the additives and finished lubricating oil can alsobe used. The additive package will typically contain one or more of thevarious additives, referred to above, in the desired amounts and ratiosto facilitate direct combination with the requisite amount of the (a)major amount of a base stock containing at least 90% by weight saturatedhydrocarbons; and (b) minor amount of a base stock selected from thegroup consisting of (i) an ester base stock wherein the ester base stockis present in an amount greater than about 10% by weight based on thetotal weight of the lubricating oil composition, (ii) an alkyl aromaticbase stock, and (iii) a base stock having an aromatic content of atleast 50% by weight wherein the base stock having an aromatic content ofat least 50% by weight is not an aromatic extract.

The trunk piston engine lubricating oil compositions of the presentinvention may be suitable for use in a 4-stroke trunk piston enginehaving an engine speed of about 200 to about 2,000 rotations per minute(rpm), e.g., about 400 to about 1,000 rpm, and a brake horse-power (BHP)per cylinder of about 50 to about 5,000, preferably about 100 to about3,000 and most preferably from about 100 to about 2,000. Engines usedfor auxiliary power generation applications or in land-based powergeneration applications are also suitable.

The following non-limiting examples are illustrative of the presentinvention.

EXAMPLES 1-5 AND COMPARATIVE EXAMPLES A-C

Trunk piston engine lubricating oil compositions were prepared as setforth below in Table 1. Each trunk piston engine lubricating oilcomposition was an SAE 40 viscosity grade with a TBN of 40 mg KOH/g. Thetrunk piston engine lubricating oil compositions of Examples 1-5 (withinthe scope of the invention) were formulated with the combination of aGroup II base oil and either (i) 30% by weight of ester base oil (ii) analkyl aromatic base oil or (iii) a base oil having an aromatic contentof at least 50% by weight, whereas the trunk piston engine lubricatingoil compositions of Comparative Examples A-C (outside the scope of theinvention) were formulated as follows: a Group I base oil alone(Comparative Example A), a Group II base oil alone (Comparative ExampleB) and the combination of a Group II base oil and 10% by weight of anester base oil (Comparative Example C).

The trunk piston engine lubricating oil compositions of Examples 1-5 andComparative Examples A-C were tested for the amount of black sludgeformation in the Black Sludge Deposit (BSD) Test. In the BSD Test, asample of test oil was mixed with 7.5 wt. % heavy fuel oil to form atest mixture. Each test mixture was pumped over a heated test plate fora specified period of time. After cooling and washing, test plates weredried and weighed. The weight of each steel test plate was determined,and the weight of the deposit remaining on the steel test plate wasmeasured and recorded as the change in weight of the steel test plate.The results of the BSD test are set forth below in Table 1.

TABLE 1 Comp. Comp. Comp. Ex. A Ex. B Ex. C Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex.5 Formulations (wt. %) (wt. %) (wt. %) (wt. %) (wt. %) (wt. %) (wt. %)(wt. %) Additives: 350 TBN Ca alkylhydroxy benzoate 9.81 9.81 9.81 9.819.81 9.81 9.81 9.81 150 TBN Ca alkylhydroxy benzoate 2.94 2.94 2.94 2.942.94 2.94 2.94 2.94 ZnDTP 0.68 0.68 0.68 0.68 0.68 0.68 0.68 0.68 Foaminhibitor 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 Group I base oil 86.53— — — — — — — Group II base oil — 86.53 76.53 56.53 76.53 56.53 76.5356.53 Ester base oil¹ — — 10.00 30.00 — — — — Alkylated aromatic baseoil² — — — — 10.00 30.00 — — FCC medium cycle oil³ — — — — — — 10.0030.00 BSD Results: 200° C./12 hr (mg) 14 46 43 20 20 15 170° C./12 hr(mg) 2 21 7 2 ¹A polyol ester available from Croda Lubricants asPRIOLUBE ® 3970. ²An alkylated naphthalene available from KingIndustries as NA-LUBE ® KR-007. ³A highly aromatic refinery streamderived by fluid catalytic cracking (aromatic content = 62%).

As the data show, the trunk piston engine lubricating oil compositionscontaining the combination of a Group II base stock and 30% by weight ofan ester base oil (Example 1) or an alkylated aromatic base stock(Examples 2 and 3) or a base stock having an aromatic content of atleast 50% by weight (Examples 4 and 5) exhibited less black sludgedeposit formation than the trunk piston engine lubricating oilcomposition containing a Group II base stock alone (Comparative ExampleB) and exhibited comparable black sludge deposit formation to a trunkpiston engine lubricating oil composition containing a Group I basestock alone (Comparative Example A). The trunk piston lubricating oilcompositions containing only a Group II base stock (Comparative ExampleB) and the combination of a Group II base stock and 10% by weight of anester base stock (Comparative Example C) demonstrated significant blacksludge deposit formation as compared to the trunk piston enginelubricating oil compositions of Examples 1-5.

It will be understood that various modifications may be made to theembodiments disclosed herein. Therefore the above description should notbe construed as limiting, but merely as exemplifications of preferredembodiments. For example, the functions described above and implementedas the best mode for operating the present invention are forillustration purposes only. Other arrangements and methods may beimplemented by those skilled in the art without departing from the scopeand spirit of this invention. Moreover, those skilled in the art willenvision other modifications within the scope and spirit of the claimsappended hereto.

1. A trunk piston engine lubricating oil composition comprising (a) amajor amount of a base stock containing at least 90% by weight saturatedhydrocarbons; and (b) a base stock selected from the group consisting of(i) an ester base stock wherein the ester base stock is present in anamount greater than 10% by weight and no greater than about 45% byweight, based on the total weight of the lubricating oil composition,and (ii) an alkylated aromatic base stock.
 2. The trunk piston enginelubricating oil composition of claim 1, wherein the base stockcomprising at least 90% by weight saturated hydrocarbons comprises atleast one of a Group II base stock, a Group III base stock or a basestock derived from a Fischer-Tropsch synthesized, waxy, paraffinichydrocarbon material.
 3. The trunk piston engine lubricating oilcomposition of claim 1, wherein the base stock comprising at least 90%by weight saturated hydrocarbons comprises at least one Group II basestock.
 4. The trunk piston engine lubricating oil composition of claim1, which is substantially free of a Group I base stock.
 5. The trunkpiston engine lubricating oil composition of claim 1, wherein the basestock (b) is an ester base stock.
 6. The trunk piston engine lubricatingoil composition of claim 1, wherein the base stock (b) is an ester basestock, wherein the ester base stock has a kinematic viscosity of about 2to about 10 cSt at 100° C.
 7. The trunk piston engine lubricating oilcomposition of claim 5, wherein the ester base stock is a polyol esterbase stock.
 8. The trunk piston engine lubricating oil composition ofclaim 1, wherein the base stock (b) is an alkylated aromatic base stock.9. The trunk piston engine lubricating oil composition of claim 8,wherein the alkylated aromatic base stock is an alkylated fused and/orpolyfused aromatic base stock.
 10. The trunk piston engine lubricatingoil composition of claim 8, wherein the alkylated aromatic base stock isan alkylated naphthalene.
 11. The trunk piston engine lubricating oilcomposition of claim 1, further comprising one or more trunk pistonengine lubricating oil composition additives selected from the groupconsisting of an antioxidant, anti-wear agent, detergent, rustinhibitor, dehazing agent, demulsifying agent, metal deactivating agent,friction modifier, pour point depressant, antifoaming agent, co-solvent,package compatibiliser, corrosion-inhibitor, ashless dispersant, dye,extreme pressure agent and mixtures thereof.
 12. A method for improvingheavy fuel oil compatibility of a trunk piston engine lubricating oilcomposition comprising a major amount of a base stock containing atleast 90% by weight saturated hydrocarbons, the method comprising addingto the trunk piston engine lubricating oil composition a base stockselected from the group consisting of (i) an ester base stock whereinthe ester base stock is present in an amount greater than 10% by weightand no greater than about 45% by weight, based on the total weight ofthe lubricating oil composition, and (ii) an alkylated aromatic basestock.
 13. The method of claim 12, wherein the base stock comprising atleast 90% by weight saturated hydrocarbons comprises at least one of aGroup II base stock, a Group III base stock or a base stock derived froma Fischer-Tropsch synthesized, waxy, paraffinic hydrocarbon material.14. The method of claim 12, wherein the base stock comprising at least90% by weight saturated hydrocarbons comprises at least one Group IIbase stock.
 15. The method of claim 12, wherein the base stock added tothe trunk piston engine lubricating oil composition is an ester basestock.
 16. The method of claim 15, wherein the ester base stock is apolyol ester base stock.
 17. The method of claim 12, wherein the basestock added to the trunk piston engine lubricating oil composition is analkylated aromatic base stock.
 18. The method of claim 17, wherein thealkylated aromatic base stock is an alkylated naphthalene.
 19. Themethod of claim 12, wherein the trunk piston engine lubricating oilcomposition further comprises one or more trunk piston enginelubricating oil composition additives selected from the group consistingof an antioxidant, anti-wear agent, detergent, rust inhibitor, dehazingagent, demulsifying agent, metal deactivating agent, friction modifier,pour point depressant, antifoaming agent, co-solvent, packagecompatibiliser, corrosion-inhibitor, ashless dispersant, dye, extremepressure agent and mixtures thereof.
 20. A method for operating a trunkpiston engine, the method comprising lubricating the trunk piston enginewith a trunk piston engine lubricating oil composition comprising (a) amajor amount of a base stock containing at least 90% by weight saturatedhydrocarbons; and (b) a base stock selected from the group consisting of(i) an ester base stock wherein the ester base stock is present in anamount greater than 10% by weight and no greater than about 45% byweight, based on the total weight of the lubricating oil composition,and (ii) an alkylated aromatic base stock.